Preparation and thermophysical properties of nano-sized Ln2Zr2O7 (Ln?=?La, Nd, Sm, and Gd) ceramics with pyrochlore structure

Rare earth zirconates (Ln₂Zr₂O₇, Ln = La, Nd, Sm, and Gd) with pyrochlore structure were prepared by hydrothermal method with polyethylene glycol as surfactant. X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy were utilized to characterize the phase structure, thermal decomposition, and morphology of the products. Qualitative analysis indicates that the as-prepared zirconates are pyrochlore-type structures. The specific surface area, lattice parameter, and average crystallite size of the as-prepared products are closely related to the ionic radius. The activation energy of crystal growth shows an increasing trend with the decrease in ionic radii. The sintering behavior of compacted body was also investigated, revealing that the sintering-resistance properties of Ln₂Zr₂O₇ are descending as the order of La₂Zr₂O₇, Nd₂Zr₂O₇, Sm₂Zr₂O₇, and Gd₂Zr₂O₇.     

燃气开环磁流体发电机的研制

介绍了磁流体发电的原理,设计制造了燃气开环磁流体发电机的实验样机。阐述了实验样机的结构和功能,总结了样机设计的要点。     

Influence of phosphorus on iron-based friction material prepared directly from vanadium-bearing titanomagnetite concentrates

In situ selective carbothermic reactions and vacuum sintering were used to prepare iron-based friction material directly from vanadium-bearing titanomagnetite c...     

核桃花中绿原酸、新绿原酸和隐绿原酸的提取工艺响应面优化及其抗氧化活性研究

目的 探讨干燥核桃花中绿原酸、隐绿原酸和新绿原酸的最佳提取工艺及其抗氧化活性。方法 采用超声波辅助乙醇法提取核桃花中的绿原酸、新绿原酸和隐绿原酸, 以提取温度、乙醇体积分数、提取时间和料液比为自变量, 以得率的总评归一值(overall desirability, OD)为因变量, 应用响应面对提取工艺进行优化, 并通过体外实验评价了其抗氧化活性。结果 最佳提取工艺为：温度77℃, 乙醇体积分数67%, 提取时间28 min, 料液比1: 23(g/mL)。此时,绿原酸、新绿原酸和隐绿原酸的总提取率最佳, OD值可达0.91, 对DPPH自由基、ABTS自由基和羟自由基的半数抑制浓度(Half-maximal Inhibitory concentrations, IC50)值分别为41.63、41.68和34.43 μg/mL。结论 优选出的工艺稳定可行, 且提取液具有较好的体外抗氧化活性, 为核桃花中绿原酸类成分的进一步开发利用提供了理论基础。     

Ag/LaNixCo1-xO3触点材料的制备及电接触性能研究

本文运用溶胶-凝胶燃烧法合成了双钙钛矿型LaNixCo1-xO3(LNCO)纳米材料,利用粉末冶金和热挤压技术制备了相应的Ag/LNCO触点材料及元件样品。重点考察了不同Ni、Co含量对Ag/LNCO触点材料微观结构、物相组成、物理性能、力学性能及电寿命服役能力的影响,对其电弧侵蚀失效行为进行了研究,并与SnO2粉体增强Ag基触点材料进行对比。结果表明:溶胶凝胶法合成的LNCO纳米颗粒粒径为20-30 nm,经粉末冶金工艺制备的Ag/LaNi0.5Co0.5O3触点材料电学性能和电寿命都优于Ag/SnO2触点材料,其电阻率低至2.10 μΩ?cm,电寿命性能达到51287次。表明Ag/LaNi0.5Co0.5O3触点材料性能较佳,是一种可以取代Ag/CdO的新型触点材料。     

定向凝固Ni3Al基高温合金IC10的760℃蠕变机理

研究了定向凝固高温合金IC10在760℃/750MPa条件下的恒载拉伸蠕变机理.结果表明:在760℃/750MPa条件下蠕变时,IC10合金组织稳定,TEM位错形貌中有反向畴和层错,位错切过γ′是合金的主要蠕变机制.蠕变裂纹均产生于γ基体和碳化物界面上,并沿着垂直于应力轴方向在基体中扩展.     

A novel ethanol gas sensor based on ZnO-microwire

One-dimensional (1D) ZnO microwires were successfully synthesized by chemical vapor deposition and their structural and morphological properties were analyzed by X-ray diffraction and scanning electron microscopy, demonstrating that the microwires were single crystalline with perfect hexagonal structure and smooth surface. Using these 1D microstructures, we fabricated a novel ZnO-based ethanol gas sensor. Operating at room temperature, the sensor was found to have good sensing characteristics. The reliability and stability of the sensor could be improved by connecting multiple 1-wire devices (1-WD) in parallel into a multi-wires device. In interior natural lighting environment and under 3 V bias, the response and recovery time of the 1-WD to 200 ppm ethanol gas were <10 s and about 300 s, respectively, and the minimum and maximum detection limit were about 2 and 200 ppm, respectively. A sensing model was proposed for discussing the performance of the sensor. The simplicity in fabrication, low power consumption and low cost make the sensor suitable for practical application in many fields, especially in identifying driving under the influence and chemical industry monitoring.     

SiAlCN前驱体低温陶瓷化过程研究

采用异丙醇铝改性氨解制备的聚甲基乙烯基硅氮烷来制备聚铝硅氮烷,研究其在200～800℃下的陶瓷化过程中所发生的结构变化.采用红外光谱(IR)、气相色谱(GC)和耦合热重/差热分析(TG/DTA)对陶瓷化过程的键变化、挥发物、热失重和差热分析进行表征.结果表明:200℃之前有吸热峰是溶剂和低聚物挥发所致,此时只有1％的质量损失;质量损失主要发生在200～600℃之间,可达28％,进一步交联成键,大量CH4,H2和NH3放出;600℃到800℃只有3％的失重,陶瓷化过程基本结束.通过IR,GC和DTA推测出陶瓷化过程可能发生的变化,XRD结果表明800℃裂解产物是非晶态物质.